Active organic matter is probably the most widely acknowledged composite indicator of soil quality. The objective of the present study was to develop a simple test of active organic matter for routine measurement of soil quality that would help evaluating impacts of management practices on agroecosystems. A wide range of soils collected from different countries of the world under variable management systems were analyzed for total C, particulate organic C, macroaggregates protected C, mineralizable C, microbial biomass C, water soluble C, glucose equivalent C, neutral 0.02M KMnO4 oxidizable C, and acid, alkali and salt extracted C concentration. Among the soil C fractions as a measure of active organic matter, the amount of soil organic matter oxidized after reacting with 0.02M KMnO4 by converting Mn (VII) to Mn(II), was significantly accounted variations (r2=0.56 to 0.83) in soil quality key indicator properties that are identifiable and measurable, sensitive to management practices, and critical for ecosystem functions. Furthermore, the oxidizable C pool significantly correlated with soil quality index (r2= 0.62), mineralizable (r2=0.46) and chemically labile (r2=0.65) N pools and crop yields (r2=0.56). A simplified field version of the active organic matter test (color chart) based on 2 minutes shaking of air-dried soil with neutral 0.02 M KMnO4 was developed by changes in the solution color from deep purple to different shades of light pink or colorless. The lighter the color or colorless of the 0.02M KMnO4 solution after reacting with soil, the greater the amount of active organic matter content and better the quality of the soil. Addition of 0.1M CaCl2 to the 0.02M KMnO4 reagent provided for rapid settling of the soil after shaking to match the color of the solution with color chart for evaluating soil quality, determining N availability, and predicting crop yields. Key words: Soil organic matter, oxidizable C, soil quality index, labile N, and crop yields.